AOBR Radiology key terms

A calibrated number expressing how strongly a tissue attenuates X-rays on CT, with water set at 0 and air near -1000; it lets observers compare tissue density objectively.

Two display settings that map the CT attenuation range onto visible gray shades; level sets the center of the range and width sets how much contrast is shown.

Increase in tissue attenuation after intravenous contrast medium, reflecting blood supply and capillary permeability; it distinguishes vascular structures and characterizes lesions.

CT or MR acquisition timed to peak arterial opacification, useful for depicting hypervascular tumors, vessel anatomy, and active bleeding before venous filling obscures them.

Acquisition of unenhanced, arterial, portal venous, and delayed liver images so that lesion enhancement patterns over time can be assessed and lesions characterized.

Loss of enhancement in a lesion on later post-contrast phases relative to surrounding parenchyma, a feature used in characterizing hepatocellular carcinoma and other tumors.

A thin enhancing rim seen around a liver lesion on delayed imaging, formed by compressed parenchyma or fibrous tissue, supporting a diagnosis of hepatocellular carcinoma.

Hazy increased lung attenuation that does not obscure underlying vessels or bronchi, indicating partial airspace filling or interstitial thickening.

Dense lung opacity that obscures underlying vessels and bronchial walls, usually from airspace fluid, pus, blood, or cells, and often showing air bronchograms.

Branching air-filled bronchi made visible against surrounding opacified lung, confirming that the opacity lies within the airspaces rather than replacing the lung.

A network of fine lines on chest imaging produced by thickened interlobular septa or intralobular interstitium, often described as septal or honeycombing patterns.

Clustered thick-walled cystic spaces in subpleural lung, usually 3 to 10 mm, representing destroyed lung architecture and a hallmark of usual interstitial pneumonia.

Vessel imaging in which a pre-contrast mask image is subtracted from contrast-filled images, removing bone and soft tissue so arteries stand out clearly.

Vascular access by needle puncture, passage of a guidewire, removal of the needle, and placement of a catheter over the wire into the vessel lumen.

Deliberate occlusion of a vessel with coils, particles, glue, or balloons to stop hemorrhage, treat vascular malformations, or devascularize tumors.

A self-limited constellation of pain, fever, nausea, and malaise following embolization, caused by tissue ischemia and inflammation rather than infection.

Delivery of a thrombolytic drug directly into a thrombus through a placed catheter to restore flow while limiting systemic bleeding risk.

Adverse events at a puncture site such as hematoma, pseudoaneurysm, arteriovenous fistula, dissection, or thrombosis, recognized by pain, swelling, or a bruit.

Delivery of radioactive microspheres into hepatic arteries to irradiate tumors locally, preceded by mapping angiography and lung shunt assessment.

Ischemic injury in the distribution of the middle cerebral artery, typically causing contralateral face and arm weakness, aphasia or neglect, and cortical signs.

Cellular swelling after ischemia with net water movement into cells, producing restricted diffusion on MRI and low attenuation with loss of gray-white differentiation on CT.

High signal on diffusion-weighted images with low apparent diffusion coefficient, indicating impeded water motion such as in acute ischemia or dense cellularity.

A calculated image derived from diffusion-weighted data that quantifies water mobility; low values confirm true restricted diffusion rather than T2 shine-through.

Bleeding into an ischemic infarct, ranging from petechial spots to a hematoma, which may cause secondary neurologic deterioration and mass effect.

Enlargement of the cerebrospinal fluid spaces from impaired flow, absorption, or overproduction, classified as communicating or noncommunicating and often causing ventricular dilatation.

Fluid seeping across the ventricular lining under pressure, seen as periventricular low density on CT or high T2 signal on MRI in acute hydrocephalus.

Shift of brain tissue across dural compartments or the skull base from mass effect, threatening the brainstem and requiring urgent decompression.

Displacement of midline brain structures measured from the septum pellucidum, indicating unilateral mass effect and risk of herniation.

Hypertrophy of the pyloric muscle in young infants causing nonbilious projectile vomiting, with an elongated narrowed pyloric channel on ultrasound.

Telescoping of proximal bowel into distal bowel, causing colicky pain and currant-jelly stools, with a target or pseudokidney appearance on imaging.

Concentric rings of differing echogenicity seen in cross-section, characteristic of intussusception or of a thickened bowel wall in inflammation.

Inflammatory necrosis of neonatal bowel, usually in premature infants, showing pneumatosis intestinalis, portal venous gas, and risk of perforation.

Gas within the bowel wall, seen as linear or bubbly lucencies, indicating severe bowel disease such as ischemia or necrotizing enterocolitis.

A fracture involving the growth plate, classified I through V by whether the break passes through physis, metaphysis, epiphysis, or a combination.

An incomplete compression fracture of the metaphysis producing a cortical bulge, common in young children whose bone is soft and pliable.

The SI unit of absorbed radiation dose, equal to one joule per kilogram; it quantifies dose delivered to tissue during radiotherapy.

Dividing a radiation dose into multiple smaller treatments, exploiting repair differences between tumor and normal tissue to improve the therapeutic ratio.

A contour on a treatment plan connecting points that receive the same dose, used to judge target coverage and dose to organs at risk.

A graph showing the percentage of a structure's volume receiving at least a given dose, used to evaluate plan quality and constraints for tumor and normal organs.

The balance between tumor control and normal-tissue injury; a favorable ratio means tumor receives a much higher dose than surrounding healthy tissue.